I see this argument come up a lot with regards to all kinds of infrastructure, and the thing is it simply _isn't true_.
What matters is population density, GDP per capita, geography, and will. A countries size doesn't matter since twice the area will, all things being equal, also give you twice the workforce to make it happen. In fact the only change a larger area typically makes is better ability to make use of economies of scale, which makes things _easier_.
The only correlation between larger countries and trouble with infrastructure is that a large country is more likely to have large areas with nearly nobody in them, but these areas also typically account for a vanishingly small percentage of the population so they don't really count when people are talking about bad infrastructure.